Theophylline hydrate: clinical use

Prescribing considerations

• Theophylline has a narrow therapeutic window and variable clearance; review comorbidities, smoking, alcohol use and interacting medicines.
• Maintain the same modified-release brand where possible because absorption can vary.
• Clearance may be reduced by older age, cardiac or hepatic disease, fever, viral infection, hypothyroidism and worsening lung disease.
• Use caution with arrhythmias, seizure disorders, peptic ulceration, severe hypertension, chronic alcohol misuse and partial urinary obstruction.

Contraindications and cautions

• Hypersensitivity to theophylline, other xanthines or product excipients
• Porphyria
• Concomitant ephedrine in children younger than six years or weighing less than 22 kg
• Theophylline use in infants younger than six months; the selected tablets are unsuitable below six years

Monitoring

• Check liver function, urea and electrolytes—particularly potassium—and smoking status before treatment.
• Measure plasma theophylline after initiation or changes and periodically once stable, following local laboratory timing requirements.
• Recheck levels when toxicity is suspected, interacting medicines are introduced or withdrawn, smoking status changes or clinical status alters.
• Consider closer monitoring in older people, pregnancy, heart failure or hepatic impairment.
• Monitor potassium in severe asthma and with other potassium-lowering treatments.

Clinical pharmacology

Theophylline is a methylxanthine bronchodilator with additional cellular anti-inflammatory effects. It is substantially protein bound, metabolised mainly in the liver and excreted largely as urinary metabolites. Clearance is influenced by age, smoking, alcohol, interacting medicines and cardiorespiratory or hepatic disease.

Formulation and product differences

• The selected product is a prolonged-release tablet and must not be broken, crushed or chewed.
• Modified-release brands can have different absorption profiles; avoid unplanned brand switching.
• Oral theophylline and intravenous aminophylline are not directly interchangeable; switching requires calculation, interaction review and plasma-level monitoring.

Modified-release tablet

Route: Oral

Strengths: 200 mg, 300 mg, 400 mg